1. Field of the Invention
This invention relates in general to demolition tools, and in particular to a rock drill attachment for an impact tool.
2. Description of the Prior Art
One type of impact tool for breaking up hard formations in mining and construction industries is shown in U.S. Pat. No. 4,103,747 issued to Finney. This tool has a reciprocating hammer that delivers blows against a working tool, such as a chisel.
In certain operations, large boulders must be dynamited into smaller pieces before the impact tool can be used to break them down to a desired size. Dynamite operations require drilling holes in rock to a depth of three feet or less. It would be an advantage to use an impact tool as a rock drill for drilling these holes, as well as using the impact tool for demolition.
Rock drills that use rotary motion and impact from a hammer or piston are known, such as those shown in the following U.S. Pat. Nos.: 3,231,028 issued to Alcock et al; 3,268,014 issued to Drew; 3,478,829 issued to Bixby; 3,685,593 issued to Amtsberg et al and 3,981,368 issued to Lundstrom et al. In some of the patents, such as in the Bixby patent, rotation can be stopped for pure impact operations. Some, such as the device shown in the Alcock et al patent, use the reciprocating motion of the hammer to compress air for delivery to the drill bit. In all of these patents the working tool is driven by a rotary mechanism that is separate from the reciprocating action of the hammer. None of these patents show a rock drill attachment for securing to an impact tool in place of the chisel. None of these show a device that directly converts the reciprocating motion of the hammer to rotation.